Abstract A common complaint reported by middle-aged patients seeking audiologic services is an emergent decline in speech-in-noise (SIN) perception. Paradoxically, many of these patients demonstrate normal hearing thresholds or mild hearing loss that is incommensurate with the severity of their complaints. The standard audiologic test battery fails to provide these patients with answers regarding the etiology of their deficits and leaves audiologists with no objective information upon which to base counseling and treatment recommendations. To improve the standard of hearing care for these patients ? a key mission of the NIDCD ? more sophisticated and easily implementable clinical tools are needed. Over the past decade, advances in hearing science have led to more sophisticated tests to understand potential SIN deficits, including those that evaluate cochlear health, neural processing, and cognition. Surprisingly, binaural hearing ? a key contributor to real-world SIN performance requiring exquisite neural temporal processing ability ? has yet to be incorporated into these clinical batteries. Recent evidence indicates that deficits in binaural hearing may begin in middle age (30-60 years) in parallel with the emergence of SIN complaints, supporting the idea that it might underlie some patients' SIN deficits. Despite a large experimental literature on psychophysical tests of binaural hearing, however, an efficient and reliable clinical assay of binaural hearing function currently does not exist. hearing goals, processing Further, hearing broad goals of this research are to 1) develop objective (electrophysiologic) indices of binaural acuity and 2) investigate relationships between these indices and SIN performance. To achieve these a comprehensive test battery including auditory evoked potentials will be used to examine neural of binaural timing cues to simple (tones) and complex (speech) stimuli in middle-aged adults. the relationship between these measures and SIN perceptual performance on tests requiring binaural will be investigated. The The long-term goal of this research is not only to understand how binaural hearing acuity influences real-world perception but to develop easily administered objective clinical tests of binaural hearing function. Such tests would improve diagnostics and would also be beneficial for verifying and fine- tuning binaural hearing aid and cochlear implant fittings. This Mentored Career Development Award will provide the mentee with additional structured training and experience in three core areas: 1) Focused research on the neurophysiology of binaural hearing, 2) Advanced training in clinical investigation (including coursework through Northwestern University Feinberg School of Medicine's Master in Clinical Investigation program), and 3) Scientific Communication. These training experiences will allow the mentee to achieve his long-term career objective of becoming an independent clinician-scientist.